Photoelectric, liquid-level inclinometer



April 3, 1951 E. F. FLINT 2,547,310

PHOTOELECTRIC LIQUID-LEVEL INCLINOMETER Filed Aug. 14, 1947 2 Sheets-Sheet 1 OF AIRCRAFT CENTER OF TURN/f Isnventor B EDWARD F. FLINT LoNmTuom/u. AXIS 0F AIRCRAFT ammeg April 3, 1951 E. F. FLINT 2,547,310

PHOTOELECTRIC, LIQUID-LEVEL INCLINOMETER Filed Aug. 14, 1947 2 Sheets-Sheet 2 POWER SUPPLY EDWARD F". FLINT Gttorneg Patented Apr. 3, 1951 PHOTO'ELE- GTRIG, LIQUID-LEVEL INGLINOMETER 1 Edward F ,Flint,, Rochester, N.v Y., assignor tor. Bausch &.-4 L mbe Optical ,7 C mpany, Rochester, N. Y; a corporation o .N w kr ApplicationlAug-ustsld, 1947, Serial No. 768,604 zgclaimsi (01.;331-209).

The present: inventionfrelatesjto inclinometers f." the; l quid,- type/and more: p rticular y; o a

relative inclinometer for indicating; the;angularity ofr-an axis; in any aircraft withreference to ap: parent ravity:.

With reference; to the use; ofi liquid; type; in-v c1inometers;to show the; attitude-pf; aircraft; it, is: well; known;v that: the; liq id is s as; the controlmed-ium is subject; t dispIacement ausedz y f r es a tm -e n the-liquidas a; r sult nz rdi ating the; controls of the; aircra t.

In; the: present: invention; it; has been deter m ne by x ensive Xpe im ntatioIiithat-an n: strumenttof theyabove type can be sol-constructed and; arranged as to; substantiallyeliminate; the undesirable displacementof; the; liquid while still providing aninstrument for v aircraftg use which has? advantages :in" instrument .;or; blind? flying. The present invention may also be applied: to other, devices and: equipment where-in, it is. de: sired Zt edetermine a: level or -anglegqof inclination with-respecttca horizontalplanea It is an object of the presentinventiorrtopro videia novel; device of theaabove typeso constructed and arranged that accuracy .'in3periorm ance is :assuredby controllingdisplacement.oi-the actuating liquid of-the;device:,

It is anotherpbject t -provide such; a: device Fig; 3, is aside view on, an.=. enlarged scale, and

partly in 1 sectioniofthe actuating memberr which is shown diagrammatically. in Rig. 1',

Fig. 4 is a deta lnin perspectiveof;theoperat; ing; parts of the, actuating member shown in, F153,;

Fig. 5 isy-a-iorce diagram relating to the-liquid element in {the inclinometer,

Fig, 6 I is a side: view of aisecond embodiment of the invention, with,-partsgin section, and

Fig. 7- is: an, electricalrcircuit diagram forthe evi e hown in F a fi-i 7 is The invention; as shown in the: embodiment ilustrated in Figs. 1-5, consists of two princilial mem r namely: n -.act:uatins; member.- fon pr ducing; electrical currents in accordanc with which is reliable, simple, and economical and :emrv

bodies aliquid columnwhichisusedxt'o control actuation of a device in responseqto movements of said liquid column. I

It is another object to; provide such a; device in which the actuating element thereofma-y;-be located in; a position of; minimum: disturbance within the;-- aircraft and may; be combined with other aircraft instruments without impairing-the accuracy and sensitiveness of. it indicatingmecm ani5m.

Still another object is to provide-an; improved device for controlling the levele attitude of instr iments and, devices; such as cameras; bomb si ht and navi ating instru en s.

Further objects 1 and advantages-will be apparent to, thoseskilledrin this; artv by referenceeto eir ol1QW e.-, description-1 and:- accomnanyin drawings in vwhich t Fig; 1- is;a .side elevation partly-in section and partly diagr mmatid f ne embod me t of he nv ntion,.

e s: 430313 2; elevatioe or: he ns rument s ew iurian changes inheightof atliquid column andanelec; tro responsiverindicating member,actuatedby the electric curr nts; theseimembers inse enera11y illustrated. at Iii? and LI respectively, The actu: ating; member Illsmayrbe 'contruetediin a variety of; designs, butnas showminiFigs; 3 31161154 iii-comp prises acontainer:, I2. having at U-shapedipart formed by vertical vside-m em1oers;; I 3-and I Moon;- nected at the: bottom by aepassagej I 5., Tha side members I3-and I mare. also connected iatrtheqtop. by;a.pass,agg-,.l [iv-so as to form, a closed-circuitrconetainen. Flow-restricting means:preferablys iii-the form;of azconstriction- I I are-located in the lower passageq- I5, Thee-container; I2 may bemaderif desire d of ransp rent 0r-1iel tr mi aa= terialsuch aseglasseon plasticcbutssuch,construce tion, is, not; exclusives. A d substantially; opaque liquid, I81 capable; of varving; the transmission of light rays. directed. therethreughis placed-iimthe container I 2 I the liquid, extending ;-p artly up, the side members I3 and; I4 toz irformliquid; :columns I e and-i 20 termimfins; n li ui is r a esi and 22; A substantially opaqu liquid of-i-the-organorsilicon oxide-class of ipolymersy satisfies theservice r quirements{inethisain rumentyto the-heeded:

vantage; hut-other;fliquidsemasgeffectivel gbemused, Since the side members I3 and I4 are connected by; the: passage I 6,; the prcessures on lthe tops of the columns- I9-and- 2 mare-substantia11r he same? Means; for directin ht} rays; hrou h h transparent;side-members; I3 i and L4 eacrossqthe topsv 2 I l and 22 :of; liquid colu nns; and Zilvdre provided comprising ;a-.: lamp: Zhhav-ing the fila ment-; 2 4 thereon substantially imalignment: with thesuriaces 2,1 and:2-2 It}; ll loeiunderstood hat he ila p- 3 Si fixed se mounted? y: suitable means not sh wn;v n is ne sized ir m battery of the liquid columns, the entire container I2 is preferably masked or covered by opaque paint or the like excepting at the windows 2'! and 28 on opposite sides of member I3 and windows 29 and 30 on opposite sides of member l4. Hence it is not necessary that the entire container be formed of a transparent material as long as it has these clear, transparent windows on both sides of the U-shaped part adjacent the top of the liquid columns.

It will be seen from the above description that the actuating member H1 in effect constitutes a pair of interconnected liquid shutters for occluding the windows through which the two bundles of light rays pass in opposite directions from the light source.

Mounted respectively adjacent to the sides l3 and I4 and substantially equidistant from lamp 23 are the light-responsive elements such as photo-voltaic cells 33 and 34 which are positioned so as to intercept light rays which emanate from the light source 23 and pass through the transparent windows and over the tops of the liquid columns l9 and 20. Supporting brackets 35 and 36 support the cells 33 and 34 opposite the windows 2'l3!l and the leads 3'', 38 and 39, 49 of Fig. 4 are fixed to the photocells 33 and 34 respectively to carry the electrical currents therefrom into the outside leads 4! and 42. The component parts of the actuating member W are enclosed in a casing 43, and are properly supported and aligned therein by suitable devices such as the clips 44.

From the foregoing, it will be apparent that the actuating member If! operates in the following manner. Inclination of the container l2 in the plane of the two columns I9 and 26 and in the direction of the arrow 0, in Fig. 3 causes the liquid column 20 to fall and the column 19 to rise with respect to the photocells. The accompanying flow of liquid [8 from One column to the other is retarded by the constriction I! in the lower passage to introduce a time delay in the liquid action so thatsudden short-duration movements will not cause an erroneous indication on the indicating member ll. As the opaque liquid in column 20 falls over the windows 29 and 30,

the light rays from the lamp 23 which strike photocell 34 are progressively increased while conversely, the light rays received by the photo-.

electric cell 33 are correspondingly decreased. The cells 33 and 34 generate a voltage response in opposition to each other, the stronger voltage predominating to cause a flow of electricit which is conducted by the leads 4| and 42 to the milliameter 5| to deflect the bar 56. When the actuating member i is in a level or normal condition, it will be apparent that both liquid columns have substantially the same height so that the light responses of both cells are substantially equal and opposite whenever the instrument is in a null position.

The indicating member [I may be constructed in the form of an individual unit or may be combined with other aviation instruments such as a turn indicator. In Fig. 1, the combined form is shown in which the indicating member I l is included in a casing 45 having two principal chambers 46 and 41 at the front and rear, respectively. The rear chamber 41 houses an air-jet operated gyroscopic turn indicating mechanism of familiar design such as illustrated in the United States patent to C. J. Crane, No. 2,280,797, dated April 28, 1942. The indicating hand 48 of the mechanism extends forwardly through the arcuate 4 opening 49 in the instrument dial In the front chamber 46, an electro-responsive device such as a milliammeter 5! is secured by any desired means, not shown, and leads 52 taken from the binding posts 53 connect with the leads 4| and 42 to actuate the milliammeter 5! by currents from the hot0-voltaic cells 33 and 34. A hand 54 projecting from the front of the milliammeter 5| through the hole 55 in the dial 50 is pivoted to swing across the dial and has a cross bar 56 mounted thereon. The dial 5% carries a horizontal fiducial line 5? which is substantially parallel to the lateral axis of the aircraft so that when the aircraft is properly banked or inclined the indicating bar 56 will be aligned parallel with the fiducial line 51.

It will be noted that the indicating member ll does not show the inclined position of the aircraft with respect to the horizon when turning an aircraft in flight but does show errors in coordination between the rudder control and the aileron control. In turning, two principal forces act on the liquid i8, namely, a gravity force directed vertically toward the earth and a centrifugal force directed outwardly from the turn parallel to the radius of turn. The resultant force obtained by composing these two forces has a direction parallel to the ver.ical axis of the aircraft When the aircraft is properly banked in turning so that line 57 and cross bar 56 on the instrument face 50 are then coincident. In this description the resultant force is otherwise known as apparent gravity. If, for instance, the aircraft is skidded around a right turn with the right wing too high for a properly coordinated turn, the right end of the cross bar 55 will be deflected upwardly above the fiducial line 5'! as shown by dotted lines in Fig. 2. The pilot is thereby notified to depress the right wing so as to regain a properly coordinated turn. Since the cross bar 56 is functionally arranged to represent the lateral axis of the aircraft, the corrective motion suggested by the position of the bar 56 relative to the fiducial line'5'l is congruent with the motion required to correct the banking position of the aircraft.

One of the important features of this invention is the placement of the actuating memberlfl in an aircraft. Experimental flight tesLing has revealed that the actuating member It should be located in the proximity of the center of gravity of the aircraft so that the liquid i8 in the actuating member is near the center of rotation of the aircraft and responds in the desired manner to abnormal flight conditions. Since the modern trend toward great size of aircraft results in locating the aircraft instrument room a great distance from the center of gravity of the craft, the actuating and indicating members of this invention are separated and only the device which is actuated by the actuating member such as the indicator member i l is located in the instrument room of the aircraft.

Locating the actuating member near the center of gravity of the aircraft, is particularly advantageous for example when this invention is used for blind flying. The usual procedure for blind flying is to turn the aircraft alternately right and left through gentle turns of short duration so as to keep the right side of the guide beam located by the audibility of the proper guiding signals. Turns with minimum bank are employed to keep the antennae of the radio signal receiver in a favorable position for good reception .of the radio tower radiations. When the tion congruent with the polarity of the current. The predominant current flow in the field circuit of the motor is, therefore, dependent on the instantaneous relative strength of the opposed rectifier and amplifier circuits. Since the armature of the motor N99 is connected directly to a D. C. source, a reversal in polarity of D. C. current flow through the field of the motor results in a reversal of the rotation of the motor.

Because of the wide range of sensitivity which is available on the above-described circuit to a change in photoelectric response of the phototubes 93 and 99 and because of the variation of the occluding action of the liquid columns by changing the setting of the diaphragms 35 and 91, the practical scope or" use of this device in an aircraft is greatly extended. Attention is called to the fact that the motor its has the same relationship to the actuating member 56 as the indicating member l i has to the actuating member 89 of the first embodiment of this invention. The servomotor I95 is arranged so that it will actuate suitable mechanism whereby the level attitude of a device such as an instrument may be maintained automatically. Thus, for example, two of the actuating members, such as shown in Figs. 4 and 6, may be mounted at right angles to each other on a platform so that the latter may be automatically maintained in level position. Instead of employing two separate actuating members, the container i2 may, for example, be provided with another pair of upright members arranged at right angles to the plane of members l3 and i4 and all inter-connected so that the liquid will extend up into all four side members. Another'pair of light-responsive cells would, of

course, need to be operatively positioned with respect to the other pair of side members.

From the foregoing, it will be apparent that I am able to attain the objects of my invention and provide a liquid type inclinometer which will be simple in structure yet efdcient in operation. My device provides an improved means for indicating the flight attitude of aircraft and also affords an improvement in apparatus for indicating angles of inclination. It can also be embodied to good advantage in an apparatus for automatically maintaining the level attitude of navigation instruments, cameras or the like. Various modifications may obviously be made without departing from the spirit of the invention as pointed out in the appended claims.

I claim:

1. A device of the type described comprising a light-tight casing having upper and lower chambers and communicating openings therebetween, a liquid container positioned in one chamber, said container having a U-shaped portion, a substantially opaque liquid in the container and forming columns extending partially up the sides of the U-shaped portion, said sides having transf8 parent windows adjacent the tops of the columns and in alignment with said openings, a light source positioned midway between the sides of the container to direct light rays across the tops of the columns, a pair of light responsive cells located in the other chamber, and optical means for directing through said openings and onto the respective cells light rays which pass across the tops of the columns, and electrical means for converting the light responses of said cells into mechanical motion as the casing is tilted in the vertical plane of the container to cause the respective columns to rise and fall and thereby decrease the light rays falling on one cell and increase the rays striking the other cell. 2. In an inclinometer, the combination of casing having upper and lower chambers and communicating passageways connecting the adjacent sides of the respective chambers, a liquid container in one chamber, said container having a U-shaped portion, a substantially opaque liquid within the container forming columns extending partially up the sides of the U-shaped portion, said sides having transparent windows adjacent the tops of the columns and in alignment with said passageways, a light source positioned-between the sides of the container to direct light rays across the tops of the columns, a pair of light responsive cells in the other chamber and in alignment with the passageways, and reflectors and lenses in the passageways for directing onto the respective cells light rays which pass across the tops of the respective columns whereby tilting of the container in a vertical plane will produce dilferent responses in the respective cells.

EDWARD F. FLINT.

REFERENCES CITED The following references are of record in the file or" this patent:

UNITED STATES PATENTS Number Name Date 1,068,116 Converse July 22, 1913 1,305,935 Rieker June 3, 1915 1,626,567 Steinbrecht Apr. 26, 1927 1,885,098 Hill Oct. 25, 1932 1,930,496 Wilson et a1. Oct. 17, 1933 1,955,315 Styer Apr. 17, 1934 2,019,871 Pettingill et al. Nov. 5, 1935 2,075,502 Carlson Mar. 30, 1937 2,252,727 Pepper Apr. 19, 1941 2,268,256 Knouse Dec. 30, 1941 2,371,383 Glenny Mar. 13, 1945 2,410,550 Padva Nov. 5, 1946 2,427,902 Clifton et al Sept. 23, 1947 FOREIGN PATENTS Number Country Date 411,775 Great Britain 1934 

